Supplementary Material for: Effectiveness of antibiotics for uncomplicated diverticulitis: A retrospective investigation using a nationwide database in Japan

Introduction: The efficacy of antibiotics for diverticulitis without abscess or peritonitis (uncomplicated diverticulitis) is controversial. We aimed to investigate the effectiveness of antibiotics for uncomplicated diverticulitis.
Methods: We collected admissions data for patients with acute uncomplicated diverticulitis using a nationwide database. We divided eligible admissions into two groups according to antibiotics initiation within 2 days after admission (antibiotic group vs. non-antibiotic group). We conducted propensity score matching and compared the rates of surgery (intestinal resection and stoma creation), in-hospital death, and medical costs between the groups. We also performed multivariate analysis to identify the clinical factors that affect surgery using data before propensity score matching.
Results: We enrolled 131,936 admissions; among these, we obtained 6061 pairs after propensity score matching. Rates of both intestinal resection and stoma creation in the antibiotic group were lower than those in the non-antibiotic group (0.61% vs. 3.09%, P < 0.0001 and 0.08% vs. 0.26%, P = 0.027, respectively). Median costs in the antibiotic group were higher than those in the non-antibiotic group (315,820 JPY vs. 300,175 JPY, P < 0.0001, respectively). Multivariate analysis showed that non-initiation of antibiotics within 2 days after admission was a clinical factor that increased the risk of intestinal resection (odds ratio [OR] = 5.19, 95% confidence interval [CI]: 4.38‒6.16, P < 0.0001) and stoma creation (OR = 2.68, 95% CI: 1.53‒4.70, P = 0.0006).
Conclusion: Our results indicated that antibiotics for uncomplicated diverticulitis expected moderate to severe disease activity may reduce the risk of intestinal resection and stoma creation. Further investigations are warranted.